The invention is based on a link element for windshield wipers.
Conventional windshield wipers have a wiper arm which is comprised of a driven fastening part, a link element that is connected to it via a hinge joint, and a wiper rod rigidly adjoining the link element. The windshield wiper also has a wiper blade, which is coupled to the wiper rod and is comprised of a support bracket system and a wiper strip secured by it. The hook-shaped end of the wiper rod engages between two side walls of the support bracket system and includes a pivot bolt. The link thus produced guides the wiper blade with the wiper strip across a vehicle window; the link element and the support bracket system make it possible for the wiper strip to adapt to a curvature of the vehicle window. A required pressure of the wiper strip is achieved by means of at least one tension spring which secures the fastening part, along with the link element, to the wiper rod by means of the hinge joint. As a rule, the tension spring is suspended with a hook-shaped end on a lateral pin on the fastening part and is suspended with the other, likewise hook-shaped end on a hanging device on the link element.
The form of the individual components of the wiper arm is influenced by different requirements and stresses. They should be embodied to be as torsionally rigid, flectionally resistant, and narrow in the field of view as possible so that the wiper blade is guided in a vibration-free and controlled fashion across the vehicle window and thereby causes little interference in the field of view. Known windshield wipers therefore have a relatively wide fastening part and a link element formed out of sheet metal, which as a rule, has a U-shaped profile that opens toward the vehicle window. Its favorable resistance moment makes it particularly torsionally rigid and it can contain the tension spring so that the spring is hidden. The link element tapers toward its connecting point with the wiper rod so that it is embodied as narrow in the field of view.
The material stresses in the wiper arm depend on various factors such as driving forces and pressing forces, their engagement points and lever arms, as well as the resistance moment of the wiper arm. Since the optimal shape not only has to be matched to the stress progressions and the deflections, but also has to take other considerations into account, such as sufficient space for the tension spring, the flow resistance in the relative wind, and in particular an impairment to visibility during wiper operation, compromises often must be made.
DE 197 35 301 A1 has disclosed a wiper arm in which sheet metal parts, e.g. the fastening part and in particular, the link element with a wiper rod formed onto it, can be folded together with various numbers of sheet metal layers on top of each other in different regions, until the material thickness required for the respective cross section is achieved. In this connection, the material can be folded over by approx. 180° once or more times or remote surface regions can be placed against one another in one or preferably more steps in order to mutually support one another. Consequently, a relatively thin metal sheet can be used to produce different regions with various material thicknesses that can be adapted to the various loads. According to the prior art, the sheet metal parts are made up of flat metal sheets. They have contour surfaces and folding surfaces. The contour surfaces are used for the basic shaping of the sheet metal part and the folding surfaces are used for fastening regions and for producing various material thicknesses.
The still flat sheet metal part for a link element is cut from a metal sheet by means of a cutting or stamping process. According to this manufacturing process, a number of link elements are disposed next to one another so that a rectangle containing the outer contour of the flat sheet metal part meets the material requirements for a link element. Depending on the embodiment of the sheet metal part, various amounts of waste are generated, because even when fold engineering is used, as a rule the flat sheet metal part tapers from the linking point with the fastening part to the free end of the wiper rod in accordance with the decreasing material stress.
The known wiper arm has a hanging device for a tension spring on the link element. This hanging device is comprised of two opposing extensions of folding surfaces pointing toward the linking end, which have holes at their ends and are bent at right angles into a central plane in the intermediary space between the side walls so that the holes congruently overlap.
DE 693 05 442 T2 has disclosed a one-layer, sheet metal linking lever for a wiper arm. Other variants for hanging elements are proposed, which have additional connecting parts embodied in the form of plates or pegs. The additional connecting parts are welded or riveted to the lateral folding surfaces of the link element, or are folded inward to form shoulders. In this embodiment, although no additional waste is generated, it results in a considerable increase in the overall manufacturing costs of the windshield wiper due to an increased number of components. In addition, it is optically unfavorable because the ends of the insertion peg for the spring do not protrude far enough into the inner space between the side walls of the U-shaped profile and therefore are visible from the outside.